diff --git a/prelude.f b/prelude.f
index 71149a3..f042258 100644
--- a/prelude.f
+++ b/prelude.f
@@ -1 +1,16 @@
-1 68 AC!
+: \ KEY 10 = 0BRANCH [ -20 , ] ; IMMEDIATE \ Now we have line comments :)
+
+\ Peripheral register addresses
+
+: TXBUF 0 ;
+: RXBUF 32 ;
+: TXHEAD 64 ;
+: TXTAIL 65 ;
+: RXHEAD 66 ;
+: RXTAIL 67 ;
+: SYSREADY 68 ;
+
+\ Set SYSREADY high to indicate prelude has finished and enable user
+\ input on the JS side.
+
+1 SYSREADY AC!